1. Field of the Invention
The present invention relates generally to universal joints. More particularly, the present invention relates to a vibration damping universal joint for use in a gear shift rod of a manual transmission for an automotive vehicle.
2. Disclosure Information
As is well known in the art, selection of gears in a vehicle with a manual transmission is done by a vehicle operator through sliding movement of a gear shift lever in the vehicle. The gear shift lever is connected to the transmission by a gear shift rod. Engine and transmission vibrations can be transmitted, with or without amplification, to the shift lever through the gear shift rod so that vibration or chattering of the shift lever can be felt by the driver. If the driver tries to forcibly dampen or prevent the chattering of the shift lever, disengagement of the shift may occur. Furthermore, when the gear shift rod comprises two or more rod portions joined by coupling joints, rotational deflection between the rod portions often gives the driver a sloppy, unprecise feel during shifting.
To overcome these problems, U.S. Pat. No. 4,872,361 proposes a shift rod having a damping body which uncouples the vibrations of the engine and transmission from the gear shift lever as well as provides precise shifting. The damping body is part of a coupling joint between two shifting rod segments of the transmission shift rod and is soft resiliently over a predetermined short distance. In the twisting direction of the shift rod, the damping body is developed to be very stiff with respect to torsion for precise selection of gears.
The damping body of the coupling joint comprises a rectangular damping plate and a metal plate surrounding the damping plate. The damping plate allows movement of the shift rod all along the longitudinal axis of the rod and is very stiff with respect to torsional movements of the rod. However, the coupling joint allows only for a single degree of freedom orientation between the transmission and the gear shift lever disposed in the vehicle. It would be advantageous to provide a coupling joint which provides for three degree of freedom orientation between the transmission and the gear shift lever of the vehicle while still providing for torsional resistance of the gear shift rod.